Table 1.
Baseline characteristics of the cohort and comparisons with all births in the study region
| Characteristics | Frequency (percentagea) | P-valuec | |
|---|---|---|---|
| Birth cohort sample (Years 2006 to 2008) n = 1565 |
Deliveries in regionb (Year 2006) n = 8608 |
||
| Gender of infant | |||
| Male | 764 (49.9%) | 4462 (51.8%) | 0.079 |
| Female | 782 (50.1%) | 4145 (48.2%) | |
| Missing data | 19 | 0 | |
| Maternal age | |||
| <20 years | 87 (5.7%) | 512 (5.9%) | 0.239 |
| 20-24 years | 325 (21.1%) | 1608 (18.7%) | |
| 25-29 years | 424 (27.6%) | 2388 (27.7%) | |
| 30-34 years | 427 (27.8%) | 2515 (29.2%) | |
| ≥35 years | 274 (17.8%) | 1584 (18.4%) | |
| Missing data | 28 | 0 | |
| Birth weight | |||
| <2500 g | 39 (2.5%) | 450 (5.5%) | <0.0005 |
| 2500-3999 g | 1266 (81.7%) | 7073 (82.2%) | |
| ≥4000 g | 244 (15.8%) | 1060 (12.3%) | |
| Missing data | 16 | 2 | |
| Gestational age at birth | |||
| <28 weeks | 0 (0.0%) | 59 (0.7%) | <0.0005 |
| 28-36 weeks | 38 (2.4%) | 536 (6.2%) | |
| 37-41 weeks | 1505 (97.2%) | 7963 (92.5%) | |
| ≥42 weeks | 6 (0.4%) | 45 (0.5%) | |
| Missing data | 16 | 4 | |
| Plurality | |||
| Singleton | 1532 (98.5%) | 8388 (97.4%) | 0.016 |
| Multiple | 24 (1.5%) | 220 (2.6%) | |
| Missing data | 9 | 0 | |
| Outcome | |||
| Live birth | 1554 (99.9%) | 8547 (99.3%) | 0.007 |
| Stillbirth | 2 (0.1%) | 61 (0.7%) | |
| Missing data | 9 | 0 | |
aPercentages are calculated based on the available (non-missing) data.
bData for the study region (Logan, Gold Coast, Beaudesert, Tweed) are provided by Queensland Health and New South Wales Health.
cChi-square test for comparing proportions between birth cohort sample and the general population.